Oct 30, 2015

Leah Remini Speaks Out on Her Break From Scientology

Leah remini taking on scientology in her new memoir, "Troublemaker: Surviving Hollywood and scientology". And she sat down with Dan Harris for a candid conversation about her break with the church after three decades. Good morning, Dan. Hey, George, good morning. In a church known for its celebrity members Leah remini is the most famous scientologist to defect and then go public. This morning we have an advanced look at her exclusive interview with ABC news. Long before she was TV royalty starring on the hit CBS sitcom "The king of queens." Do you need to build yourself up by tearing me down.

Reporter: Leah remini was a child who joined scientology at the behest of her mother, who to use church terminology brought her daughter into the faith and put her on course. What does that mean go on course? You learn how to aply the techniques of scientology to yourself and others. Reporter: So for a kid who was always looking around comparing herself to other people, to be part of a faith where you had a mission to save -- The planet, save the planet. That must have been a big deal. Yes, and because scientologists view children as spiritual being you're not treated as a kid so you're given a lot of responsibility. Your ego becomes extremely inflated. Reporter: Leah would go on to be an active member for more than three decades. I love it. I love being involved with it because I feel like I'm a good person. Reporter: But as she describes in her new book, "Troublemaker," she would ultimately leave the faith and level some scathing and very public criticisms. The decision to leave is you're giving up everything you have ever known and everything you have worked for your whole life. I feel that people need to understand this is my whole life. I want them to understand how it happens. Reporter: It is quite a yarn she has a lot to say and we'll have. More of the story behind her decision to leave and publicly criticize the church in which she was raised tomorrow right here on "Gma" and you can see our full exclusive interview Friday night on "20/20." Her whole life. Wow. . Of it, yep. Thanks very much.

This transcript has been automatically generated and may not be 100% accurate.http://abcnews.go.com/GMA/video/leah-remini-speaks-break-scientology-34818433